Biology Evolution Exam 3 Questions & Answers

Where are substitutions more common? - ANSWERSat positions that do not change the amino acid What does neutral mean? - ANSWERSdon't convey a selective advantage or disadvantage What does the molecular clock do? - ANSWERShelps you calculate how long it has been since two species "diverged" from a common ancestor What is positive directional selection? - ANSWERSrate of non-synonymous substitution exceeds the rate of synonymous substitution What is neutral selection? - ANSWERSrate of non-synonymous substitution equals the rate of synonymous substitution What is a form of stabilizing or purifying selection? - ANSWERSrate of non-synonymous substitution is less than the rate of synonymous substitutions Where is genetic drift stronger: smaller or larger populations? - ANSWERSsmall populations What does sexual recombination lead to? - ANSWERSleads to genetic variability in offspring What are some of the disadvantages of sexual reproduction? - ANSWERSonly 50% of the female genes are passed on; recombination separates adaptive gene combinations What are the advantages of sexual reproduction? - ANSWERSrecombinations can separate deleterious combinations; homologous chromosomes are used to repair damaged DNA; recombination introduces genetic variation What is the main advantage of asexual reproduction? - ANSWERSincreased fitness What are some of the disadvantages of asexual reproduction? - ANSWERSno way to eliminate deleterious mutations What is lateral or horizontal gene transfer? - ANSWERSprocess by genes, organelles, or fragments of entire genomes move from one lineage to another What is gene duplication? - ANSWERSentirely new copy of a gene appears in a genome over evolutionary time What is a gene family? - ANSWERSgroup of homologous genes that have related functions What is speciation? - ANSWERSprocess in which biological lineages diverge due to reproductive isolation, resulting in new species What are sister species? - ANSWERSeach one is the other's closest relative What is the morphological species concept? - ANSWERSdefines a species based on observable morphological characteristics such as body shape, size, color, and other structural features What are some of the problems of the morphological species concept? - ANSWERSmembers of the same species may look alike; members of the different species may look similar What is the biological species concept? - ANSWERStwo organisms are of the same species if they can mate with one another What is the main idea of the biological species concept? - ANSWERSgroups of actually or potentially interbreeding natural populations that are reproductively isolated What is reproductive isolation? - ANSWERSsituation in which two groups of organisms are unable to exchange genes What are the disadvantages of the biological species concept? - ANSWERSdoes not apply to asexual organisms; cannot be applied to extinct species; ring species are too distantly related to interbreed What is the lineage species concept? - ANSWERStwo groups that share a branch on the tree of life What does speciation require> - ANSWERSrequires an interruption in gene flow What does the Dobzhansky-muller model explain? - ANSWERSexplains how a single lineage can split into two reproductively isolated species; overtime, the two species will be unable to mix and will be considered two different species When does reproductive isolation increase? - ANSWERSwhen a species diverges genetically What is allopatric speciation? - ANSWERSpopulation is divided by a physical or geographic barrier, forming two reproductively isolated populations that evolve independently What is sympatric speciation? - ANSWERSspecies arise from a population that remains connected What does disruptive selection do? - ANSWERSfavors two extreme phenotypes and results int eh divergence between two species What is temporal isolation? - ANSWERSflower at different times; breed at different times of the year What does polyploidy mean? - ANSWERSmistake during cell division results in an individual with cells that have more than one copy of teh genome autopolyploidy - ANSWERSduplication of a set of chromosomes in a single species allopolyploidy - ANSWERSchromosomes of two different species are combined incipient species - ANSWERSspecies that are in the process of diverging into separate species, but can currently interbreed What is a prezygotic isolating mechanism? - ANSWERSprevents hybridization; prohibits individuals of different species from attempting to mate What is mechanical isolation? - ANSWERSsome animals are simply not physically compatible with other animals due to anatomical differences What is temporal isolation? - ANSWERSnever have the opportunity to reproduce with the other due to the timing of reproduction What is behavioral isolation? - ANSWERSpairing of mates does not occur unless the correct mating rituals or signals are performed (certain frogs will only mate with individuals who make a specific kind of mating call) habitat isolation - ANSWERSsome animals are isolated by space such that they never have the opportunity to come into contact with one another What is gametic isolation? - ANSWERSsome animals produce sperm and eggs that simply will not fuse when they come into contact (important in aquatic communities) What is a postzygotic isolating mechanism? - ANSWERSreproductive barriers that prevent interbreeding after the development of the zygote; reduce the fitness of the hybrid offspring What are some of the post-zygotic mechanisms? - ANSWERSreduced genetic compatibility; low hybrid zygote viability; low adult hybrid viability; hybrid infertility Why does natural selection tend to favor pre-zygotic mechanisms? - ANSWERSit is easier to prevent reproduction from occurring in the first place Where are pre-zygotic reproductive barriers stronger? - ANSWERSpopulations living in sympatry have stronger reproductive barriers because they prevent hybridization from occurring (hybridization already occurs in allopatric speciation) What does a phylogeny do? - ANSWERSdescribes the evolutionary history of the relationships between living things What is a node? - ANSWERSpoint where two branches separate What does the root represent in a phylogenetic tree? - ANSWERScommon ancestor that all organisms share What may or may not mean something on a phylogenetic tree? - ANSWERSbranch length What is special about the order of things on a phylogenetic tree? - ANSWERSnodes can spin around; you can swivel the branches at the top node without changing the relationships What is a taxon? - ANSWERSgroup of species with a name What is a sister species? - ANSWERSspecies that directly evolve from a common ancestor monophyletic clades - ANSWERSgroups of taxa that include an ancestor and all of its descendants What are sister clades? - ANSWERStwo clades that are each other's closest relatives what is systematics? - ANSWERSstudy and classification of biodiversity What is homology? - ANSWERSany heritable trait shared by more than one species and inherited from a common ancestor What is a derived trait? - ANSWERSevolved from an earlier condition What is a synapomorphy? - ANSWERSshared, derived traits that provide evidence of common ancestry